CSF Leak, Meningitis Flashcards
What produces and absorbs CSF, and how much is produced a day? What is normal CSF pressure?
Ependymal cells of choroid plexus produces 600-700cc of CSF a day. Flows down through the foramina of luschka and magendie. Absorbed by arachnoid villi in dural venous sinuses.
Normal CSF pressure 4cmH2O in infants to 14cmH2O in adults (balance of secretion and absorption)
What are two routes of access for middle ear infection into the inner ear?
- Round window (most common)
- Oval window
Although rare in comparison to the frequency of middle ear infections, this route is likely the most common for spread to the inner ear
What is Hyrtl’s fissure?
- A congenital infralabyrinthine fissure through the petrous temporal bone
- Very rare cause of spontaneous CSF otorrhea and recurrent meningitis
What are three routes of access for meningeal infections into the inner ear?
- Cochlear aqueduct (scala media to Posterior cranial fossa)
- Internal auditory canal (lamina cribrosa - thin wall of the IAC, with a medial bony projection which is the falciform crest)
- Spiral modiolar vessels (arising from the labyrinthine artery, off the anterior inferior cerebellar artery)
What are 4 possible paths of intracranial spread of acute otitis media?
- Persistent Hyrtl’s fissure
- Hematogenous (most common)
- Direct spread (e.g. through bony defecft in tegmen)
- Through Labyrinth/IAC
What are the signs and symptoms of meningitis?
SYMPTOMS:
1. Headaches
2. Photophobia
3. Phonophobia
4. Lethargy
5. Fevers
6. Altered LOC
SIGNS:
1. Kernig’s sign: Resistance or pain with knee extension
2. Brudzinski’s Sign: Reflex flexion of both hips and knees when the neck is passively flexed
3. Nuchal rigidity
What are the factors that may increase the risk of developing meningitis secondary to ear infections/ear disease?7
- Enlarged vestibular aqueduct
- Perilymphatic fistula
- Persistent Hyrtl’s fissure
- Temporal bone fracture
- Tegmen defect
- Cochlear malformation (E.g. Mondini)
- Prior cochlear implantation
What is the best imaging to evaluate or look for intracranial abscess or complications?
- MRI with gadolinium
- CT can often miss early intracranial findings
What are 8 causes of labyrinthitis ossificans?
- Meningitis
- Labyrinthitis (serous or suppurative)
- Labyrinthectomy
- Cochlear implantation
- Temporal bone trauma
- Advanced otosclerosis
- Autoimmune
- Vascular occlusion
V-MASCOTS
V: Vascular occlusion
M: Meningitis
A: Autoimmune
S: Suppurative or serous labyrinthitis
C: Cochlear implantation
O: Otosclerosis advanced
T: Temporal bone trauma
S: Surgery (or medical) (Labyrinthectomy)
What are the most common causes of bacterial meningitis, and what is the incidence of hearing loss with meningitis?
- Streptococcus pneumoniae - 20%
- Haemophilus influeza prior to Hib vaccine
- Primary fungal - Aspergillus, Cryptococcus, Candida
- HIV meningitis (+SSNHL) - Cryptococcus
Incidence of hearing loss = 20%
How do you determine the type of meningitis based on CSF sampling?
Based on Gross appearance, proteins (mg/dl), glucose (mg/dl), and cells/cubic mm
NORMAL:
- Gross: clear
- Proteins: 15-40
- Glucose: 50-80
- Cells/cmm: 0-5 lymphocytes
BACTERIAL:
- Gross: Cloudy
- Proteins: 60-1000
- Glucose: 0-45
- Cells/cmm: 1000-50000 mostly neutrophils
ASEPTIC (VIRAL):
- Gross: Clear
- Proteins: Normal or increased
- Glucose: Normal
- Cells/cmm: 100-1000 mostly lymphocytes
TB:
- Gross: clear/clot
- Proteins: Moderate 45-300
- Glucose: Normal or decreased
- Cells/cmm: 10-1000
What are the possible etiologies for CSF otorrhea?
- Traumatic - 90% will close spontaneously
- Surgical/iatrogenic (16%)
- High intracranial pressure (e.g. tumors, hydrocephalus)
- Normal intracranial pressure entities (e.g. Congenital, spontaneous, osteitis/osteomyelitis)
What are 7 congenital causes of CSF otorrhea?
- Bony tegmen defect (most common congenital cause, but present lateral in life)
- Arachnoid granulations (“spontaneous”, also present later in life)
- Mondini malformation
- Enlarged cochlear aqueduct (perilymph)
- Enlarged fallopian canal
- Patent Hyrtl’s fissure - transient anatomic landmark in the developing fetal petrous temporal bone and is usually closed by the normal progression of ossification in the 24th week of gestation.
- Petromastoid canal fissure - subarcuate artery and vein
- Preformed bony pathway with increased subarachnoid pressure transmitted
- Generally present early in life with meningitis or non-clearing serous otitis media
- This is the reason why the scala tympani ossifies
Vancouver 304
What are some tests to identify CSF fluid (e.g. CSF otorrhea/rhinorrhea)?
CLINICAL SIGNS/TESTS:
1. Clear, non-sticky, nasal/aural discharge associated with head tilting (gravity dependent) or straining
2. Halo sign of fluid
MICRO TESTS:
1. Test fluid for glucose and protein content
2. Beta2 transferrin - Almost exclusively found in CSF, but also found in perilymph, aqueous and vitreous humor
- Most sensitive measure of identifying CSF
- Need 0.5-5mL of fluid for testing
IMAGING:
1. CT Cisternography
2. MRI Cisternography (T2 weighted images with fat suppression and image reversal) - does not require an active leak, avoids contrast
3. Intrathecal Fluorescein (0.1cc of 10% fluorescein in 10cc of CSF) with or without blue light endoscopy - inject into subarachnoid space and used to identify leaks intraoperatively
What are the side effects of intrathecal fluorescein?
- Cardiac arrhythmias
- Seizures
- Headaches
- Cranial nerve defects (off-label in the US)
